Lithium batteries can be divided into two categories: disposable non rechargeable batteries and rechargeable batteries (also known as batteries).
Non rechargeable batteries, such as lithium manganese dioxide battery and lithium thionamide battery.
Rechargeable batteries can be divided into the following categories according to different situations.
1. Divided by appearance: square lithium battery (such as ordinary mobile phone battery) and cylindrical lithium battery (such as 18650 of electric tools);
2. According to outsourcing materials: aluminum shell lithium battery, steel shell lithium battery and soft pack battery;
3. According to cathode materials: lithium cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), ternary lithium (linixcoymnzo2), lithium iron phosphate (LiFePO4);
4. According to electrolyte state: lithium ion battery (LIB) and polymer battery (PLB);
5. Divided by purpose: ordinary battery and power battery.
6. According to performance characteristics: high capacity battery, high rate battery, high temperature battery, low temperature battery, etc.
（4） Interpretation of common terms
1. Capacity
It refers to the amount of electricity that can be obtained from lithium battery under certain discharge conditions.
We learned physics in high school that the formula of electric quantity is q = I * t, the unit is Coulomb, and the capacity unit of battery is specified as ah (ampere hour) or MAH (milliampere hour). It means that when the 1Ah battery is fully charged, it can be discharged with 1A current for 1 hour.
In the past, the battery of Nokia's old mobile phones (like bl-5c) was generally 500mah, but now the battery of smart phones is 800 ~ 1900mAh, the battery of electric bicycles is generally 10 ~ 20Ah, and the battery of electric vehicles is generally 20 ~ 200ah.
2. Charge rate / discharge rate
It indicates how much current to charge and discharge. It is generally calculated by multiple of the nominal capacity of the battery, which is generally called several C.
For example, for a battery with a capacity of 1500mah, 1c = 1500mah. If it is discharged at 2c, that is, at 3000ma, 0.1C is charged and discharged at 150mA.
3. Voltage (OCV: open circuit voltage)
The voltage of the battery generally refers to the nominal voltage (also known as rated voltage) of the lithium battery. The nominal voltage of ordinary lithium battery is generally 3.7V, and we also call its voltage platform 3.7V. When we say voltage, we generally refer to the open circuit voltage of the battery.
When the battery capacity is 20 ~ 80%, the voltage is concentrated at about 3.7V (about 3.6 ~ 3.9v). If the capacity is too high or too low, the voltage changes greatly.
4. Energy / power
The battery discharges according to a certain standard. The energy (E) that the battery can release is in wh (watt hour) or kWh (kilowatt hour), and the other 1kwh = 1 kwh.
There is a basic concept in the physics book, e = u * I * t, which is also equal to the battery voltage times the battery capacity.
The formula of power is, P = u * I = E / T, which represents the energy that can be released per unit time. The unit is w (watt) or kW (kilowatt).
Like a battery with a capacity of 1500mah, the nominal voltage is generally 3.7V, so the corresponding energy is 5.55wh.
5. Internal resistance
Because charge and discharge can not be equivalent to an ideal power supply, there is a certain internal resistance. Internal resistance consumes energy. Of course, the smaller the internal resistance, the better.
The internal resistance of the battery is in milliohm (m Ω).
Generally, the internal resistance of the battery is composed of ohmic internal resistance and polarization internal resistance. The size of the internal resistance is affected by the material, manufacturing process and structure of the battery.
6. Cycle life
Battery charging and discharging once is called a cycle. Cycle life is an important index to measure battery life performance.
IEC standard stipulates that the lithium battery of mobile phone shall be discharged to 3.0V at 0.2C and charged to 4.2V at 1C. After 500 cycles, the battery capacity shall remain more than 60% of the initial capacity. In other words, the cycle life of lithium battery is 500 times.
The national standard stipulates that after 300 cycles, the capacity shall maintain 70% of the initial capacity. When the battery capacity is lower than 60% of the initial capacity, it is generally considered to be scrapped.
7. Depth of discharge (DoD)
It is defined as the percentage of the capacity discharged by the battery in the rated capacity.
Generally, the deeper the discharge depth of lithium battery, the shorter the battery life.
8. Cut off voltage
The termination voltage is divided into charge termination voltage and discharge termination voltage, that is, the voltage at which the battery can not continue to charge or discharge. Continuing to charge or discharge under the termination voltage has a great impact on the service life of the battery.
The charge termination voltage of lithium battery is generally 4.2V and the discharge termination voltage is 3.0V.
Deep charging or deep discharging of lithium batteries exceeding the termination voltage is strictly prohibited.
9. Self discharge rate
It refers to the decline rate of battery capacity during storage, expressed as the percentage of capacity decline per unit time.
The self discharge rate of general lithium battery is 2% ~ 9% / month.
10. SOC(State of Charge)
It refers to the percentage of the remaining power of the battery and the total power that can be discharged, 0 ~ 100%. Reflect the remaining battery power
